ASP.NET WebForms - VB.NET and SignalR - asp.net

Question

This is my Hub code (very simple):
Imports System
Imports System.Web
Imports Microsoft.AspNet.SignalR
Imports Microsoft.AspNet.SignalR.Hubs
Imports Microsoft.AspNet.SignalR.Client
Imports Microsoft.AspNet.SignalR.Messaging
Imports System.Threading.Tasks
Namespace SignalRChat
Public Class ChatHub
Inherits Hub
Public Sub Send(userName As String, message As String)
Clients.All.broadcastMessage(userName, message)
End Sub
End Class
End Namespace
This is my Aspx page code:
Imports System.Web.UI.WebControls
Imports Microsoft.AspNet.SignalR.Client
Imports System.Threading.Tasks
Public Class WebForm9
Inherits System.Web.UI.Page
Public Shared hubConnection As HubConnection
Public Shared chatHubProxy As IHubProxy
Public Sub MyChat_init(sender As Object, e As EventArgs) Handles Me.Init
If IsPostBack = False Then
hubConnection = New HubConnection("https://localhost:44343/")
hubConnection.TraceLevel = TraceLevels.All
hubConnection.TraceWriter = Console.Out
chatHubProxy = hubConnection.CreateHubProxy("ChatHub")
hubConnection.Start().Wait()
End If
chatHubProxy.On(Of String, String)("broadcastMessage", Sub(ByVal userName As String, ByVal message As String)
Dim li As ListItem = New ListItem
li.Value = userName & " - " & message
li.Text = userName & " - " & message
ListBox1.Items.Add(li)
End Sub)
End Sub
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
chatHubProxy.Invoke("Send", "Io", "Messaggio")
End Sub
End Class
I made a lot of tries but always ended up with no result... I added the postback checking because I noticed I was having the connection to the hub starting and starting again on each button_click...
By the way, if I add in the same project a page with JScript code I can catch all the messages sent on the JScript code, but none of the messages sent from the html page is catched by the aspx codebehind...
It's really strange because if I take away the listbox.items.add method and I put a "MsgBox" instead, then it fires up and work... but I have found no way to manage the "messages" from my codebehind and so update controls on my page... Maybe it's a connection mistake? Did anyone of you has any experience with SignalR and WebForms with VB.NET codebehind?

Answer 1

If this helps, I have a working client code (for testing purposes) in VB.NET WinForms app. (My Hub is in C#):
Hub (ASP.NET Core in net5.0 - created using Gerald Versluis' tutorial: https://www.youtube.com/watch?v=pDr0Hx67guk):
using Microsoft.AspNetCore.SignalR;
using System;
using System.Threading.Tasks;
namespace SignalR.Hubs;
public class OneHub : Hub
{
public async Task SendMessage(Message message)
{
Console.WriteLine($"{message.SentDateTime} Sender : {message.SenderId} - {message.MessageText}");
await Clients.All.SendAsync("MessageReceived", message);
}
}
WinForms (net4.8):
Imports Microsoft.AspNetCore.SignalR.Client
Imports SignalRWinForms.Client.Messaging.Models
Public Class Form1
Private connection As HubConnection
Sub New()
InitializeComponent()
connection = New HubConnectionBuilder().WithUrl("http://192.168.1.230:5296/chat").Build()
connection.On(Of Messages)("MessageReceived", Sub(Messages)
Invoke(Sub()
ReceiveMessage(Messages)
End Sub)
End Sub)
connection.StartAsync()
End Sub
Private Sub ReceiveMessage(msg As Messages)
chatMessages.Text &= $"{Environment.NewLine}{msg.MessageText}"
End Sub
Private Async Sub btnSendMessage_Click(sender As Object, e As EventArgs) Handles btnSendMessage.Click
Dim message = New Messages With {
.MessageText = txtMessage.Text,
.SenderId = 1111,
.ReceiverId = 2222,
.Token = "token",
.SentDateTime = DateTime.Now
}
Await connection.InvokeCoreAsync("SendMessage", args:={message})
txtMessage.Text = String.Empty
End Sub
End Class
Form1 is very simple - chatMessages label to populate messages, txtMessage textbox to write message and a btnSendMessage button.
Messages Class (common for both projects)
Public Class Messages
Public Property SenderId As Integer
Public Property ReceiverId As Integer
Public Property MessageText As String
Public Property Token As String
Public Property SentDateTime As DateTime
End Class